[Enhancement] order layers by dataset

[hodoje]

This PR addresses the issue: #1658
And also it relies on #1665

Here are some component diagrams showing the current and future component layout

How things look now:

List view with two datasets and two layers (one per dataset):

Sort by dataset view for the same datasets and layers:

Clicking on the AddLayer button will open a dropdown list that will list all the loaded datasets and clicking on one of the items will create an empty layer for the selected dataset:

Did the same thing for the second dataset:

How the order looks when in list view:

When in list view the layers are sortable so after some sorting, we now have this in list view:

Which in sort by dataset view looks like this:

[heshan0131]

Please add UI screenshots for this PR, essentially showing what UI has changed, and how it looks like now

[hodoje]

Please add UI screenshots for this PR, essentially showing what UI has changed, and how it looks like now

I thought the screenshots in the issue itself were enough.
Will add more screenshots.

[heshan0131]

Please add UI screenshots for this PR, essentially showing what UI has changed, and how it looks like now

I thought the screenshots in the issue itself were enough. Will add more screenshots.

UI mockup might look different than the actual implementation

[hodoje]

Please add UI screenshots for this PR, essentially showing what UI has changed, and how it looks like now

I thought the screenshots in the issue itself were enough. Will add more screenshots.

UI mockup might look different than the actual implementation

True.

[heshan0131]

The dataset selector dropdown should look the same as the datasource selector shown below

To render a dropdown with search option use Typeahead

<Typeahead
  displayOption={displayOption}
  getOptionValue={getOptionValue}
  onOptionSelected={onSelectScale}
  customListItemComponent={DatasetItem}
  searchable={true}
  // ... other props also needed
/>

[heshan0131]

disable sortable handle in the order by dataset view